Optical fiber fan-out assembly with ribbonized interface for mass fusion splicing, and fabrication method

ABSTRACT

An optical fiber fan-out assembly includes multiple optical fibers arranged in a one-dimensional array in a transition segment in which spacing between fibers is varied from a first pitch (e.g., a buffered fiber diameter of 900 μm) to a second pitch (e.g., a coated fiber diameter of 250 μm). A polymeric material encapsulates the optical fibers in the transition segment, and the assembly further includes multiple optical fiber legs each terminated with a fiber optic connector. Optical fibers extending beyond a boundary of the polymeric material are subject to being mass fusion spliced to another group of multiple optical fibers, and the fusion splices encapsulated with polymeric material, to form a fiber optic cable assembly. Methods for fabricating multi-fiber assemblies providing fan-out functionality are further provided, and the need for furcation tubes is avoided.

PRIORITY APPLICATION

This application claims the benefit of priority of U.S. ProvisionalApplication No. 62/728,317, filed on Sep. 7, 2018, the content of whichis relied upon and incorporated herein by reference in its entirety.

BACKGROUND

The disclosure relates generally to ribbon-type fiber optic cableassemblies, and more particularly to ribbon-type optical fiber fan-outassemblies as well as cable assemblies incorporating such fan-outassemblies, in addition to methods for fabricating ribbon-type opticalfiber fan-out assemblies and associated cable assemblies incorporatingthe same with protected fusion splices.

Optical fibers are useful in a wide variety of applications, includingthe telecommunications industry for voice, video, and data transmission.In a telecommunications system that uses optical fibers, there aretypically many locations where fiber optic cables, which carry theoptical fibers, connect to equipment or other fiber optic cables. Fiberoptic cables are frequently produced by extruding thermoplastic material(e.g., polyvinylchloride (PVC)) over at least one coated optical fiber.

FIG. 1 is a cross-sectional view of an exemplary coated optical fiber 10that includes a glass core 12, glass cladding 14 surrounding the glasscore 12, and a multi-layer polymer coating 20 (including an innerprimary coating layer 16 and an outer secondary coating layer 18)surrounding the glass cladding 14. The inner primary coating layer 16may be configured to act as a shock absorber to minimize attenuationcaused by any micro-bending of the coated optical fiber 10. The outersecondary coating layer 18 may be configured to protect the innerprimary coating layer 16 against mechanical damage, and to act as abarrier to lateral forces. The outer diameter of the coated opticalfiber 10 may be about 200 μm, about 250 μm, about 250 μm or less, or anyother suitable value. Optionally, an ink layer (e.g., having a thicknessof about 5 μm) may be arranged over the outer secondary coating layer 18of the coated optical fiber 10 to color the fiber (e.g., as is commonlyused in ribbonized fibers), or a coloring agent may be mixed with thecoating material that forms the outer secondary coating layer 18.Optionally, an additional buffer (not shown) may be arranged over thecoated optical fiber 10 to provide additional protection and allow foreasier handling, effectively forming a cable. The buffer may be embodiedin a layer of different material applied to the coating 20, therebyforming a “tight buffer” closely surrounding (intimately contacting andconforming to) the coating 20. Alternatively, the buffer may be embodiedin a pre-formed tube (also known as a furcation tube or buffer tube)that has an inner diameter larger than the coating 20 and into which thecoated optical fiber 10 is inserted, thereby forming a “loose buffer.”This additional buffer typically has an outer diameter of about 900 μm.

In this disclosure, the term “optical fiber” (or “fiber”) will be usedin a generic sense and may encompass bare optical fibers, coated opticalfibers, or buffered optical fibers, as well as optical fibers includingdifferent sections corresponding to these fiber types, unless it isclear from the context which of the types is intended. “Bare opticalfibers” (including “bare glass optical fibers”) or “bare sections” arethose with no coating present on the fiber cladding. “Coated opticalfibers” or “coated sections” include a single or multi-layer coating(typically an acrylic material) surrounding the fiber cladding and havea nominal (i.e., stated) diameter no greater than twice the nominaldiameter of the bare optical fiber. “Buffered optical fibers” or“buffered sections” are coated optical fibers with an additional bufferthat increases the nominal diameter of the optical fiber to more thantwice the nominal diameter of the bare optical fiber, with 900 μm beingthe most typical nominal diameter. Buffered optical fibers may also bereferred to as “buffered cables.” As noted above, the buffer may beembodied in a layer of material applied to the coated optical fiber soas to be in intimate contact with the coating and form a “tight bufferedoptical fiber” (also referred to as “tight buffered cable”), or in aloose-fitting tube that receives the coated optical fiber to form a“loose tube” or “loose buffered” optical fiber (also referred to as“loose tube cable” or “loose buffered cable”). A gap exists between atleast a portion of the outer surface of the coated fiber and an innersurface of the loose-fitting tube, with such gap optically being filledwith a gel, powder, or some other material that facilitates insertion ofthe coated optical fiber. Finally, the term “unbuffered optical fibers”refers to optical fibers without a buffer, and therefore may encompasseither bare optical fibers or coated optical fibers.

Groups of coated optical fibers (e.g., at least 4, 8, 12, or 24 opticalfibers) may be held together using a matrix material, intermittentinter-fiber binders (“spiderwebs”), or tape to form “optical fiberribbons” or “ribbonized optical fibers” to facilitate packaging withincables, with each fiber having a different color for ease ofidentification. For example, ribbonized optical fibers are widely usedin cables for high capacity transmission systems. Some modern cables inlarge-scale data center or fiber-to-the-home networks may contain up to3,456 optical fibers, and cables having even higher optical fiber countsare under development. Buffered fibers can also be ribbonized over shortlengths by removing the buffer and holding the fibers at an appropriatepitch using the matrix material. The purpose of such ribbonization is tofacilitate termination using mass fusion splicing or multi-fiberconnectors.

In many network locations, such as data centers and fiber distributionhubs, each fiber in a ribbon may need to be terminated by a fiber opticconnector for interfacing with a transceiver or other equipment.Conventionally, a device known as a ribbon fan-out kit (RFK) enables thetransition from an optical fiber ribbon or cable to individual fibers,which are frequently inserted into furcation tubing (e.g., having a 900μm diameter) for ease of handling. In addition to furcation tubes, a RFKtypically provides a housing to receive the optical fiber ribbon, aswell as a cavity for bare fibers or coated fibers separated from theribbon to spread from a small pitch (typically 0.25 mm) into a muchlarger pitch required by the presence of the furcation tubes into whichthe individual fibers have been respectively inserted.

A conventional RFK is disclosed in U.S. Pat. No. 7,461,981 assigned toCorning Optical Communications LLC. An exploded (i.e., unassembled)perspective view of an RFK embodiment of such patent is reproduced inthe accompanying FIG. 2. The RFK 30 includes a lower furcation body 32,an upper furcation body 34, a heat shrink 36, an insert block 38, and anultraviolet (UV) indicator 40 that is sensitive to UV light. The RFK 30receives an optical fiber ribbon 42 adjacent a first end 44 of the RFK30 and separates optical fibers of the optical fiber ribbon 42 intoindividual optical fibers 48 each encased within respective furcationtubes 50 (e.g., typically having an outer diameter of 900 μm) adjacent asecond end 46 of the RFK 30. The upper and lower furcation bodies 34, 32may be molded of a rigid plastic or composite material and may definelower and upper ribbon guides 52, 54 for supporting and guiding theoptical fiber ribbon 42 into a lead-in area 56. The lower furcation body32 includes a medially arranged funnel area 58 defined between angledwalls 60 for smoothly transitioning individual optical fibers 48 of themulti-fiber optical ribbon 42 from the heat shrink 36 to the insertblock 38 without introducing appreciable attenuation due to bending ofthe optical fibers 42. The heat shrink 36 is a heat shrinkable tube thathas been mechanically expanded to provide a wide passage 62 enabling theheat shrink 36 to slide over the optical fiber ribbon 42 in a loose-fitconfiguration. After heating to shrink the heat shrink 36 around theoptical fiber ribbon 42, the heat shrink 36 promotes mechanicalretention of the optical fiber ribbon 42 in the lead-in area 56. Theinsert block 38 defines passageways 64 through which the individualoptical fibers 48 are threaded into the furcation tubes 50. Flexiblelocking latches 66 of the lower furcation body 32 are configured to bereceived by recesses 68 in the upper furcation body 34 for securement ofthe two furcation bodies 32, 34. A fill port 70 in the upper furcationbody 34 may be used to receive an epoxy or acrylate and deliver suchsubstance to the funnel area 58 to prevent movement of the opticalfibers 48 therein. Through holes 72 defined in the upper and lowerfurcation bodies 34, 32 permit the RFK 30 to be mechanically secured toan optical device or optical hardware using twist ties or cable ties(not shown). The furcation tubes 50 and the optical fibers 48 thereinmay be terminated with suitable single-fiber or multi-fiber connectors(not shown) to form furcated connector pigtails.

Direct termination of individual furcated fibers spreading outward froma ribbon with single-fiber connectors can be a cumbersome process.Optical fibers must be individually routed through separate furcationtubes, which is particularly time-consuming. The friction of a furcationtube limits the length of a furcated connector pigtail. Low frictionfurcation tubes are made of polytetrafluoroethylene (PTFE), which is acostly material and can represent a significant fraction of the cost ofa cable assembly. After optical fibers are routed through furcationtubes, connectors are then attached (often manually) to distal ends ofthe individual optical fibers and furcation tubes to form the furcatedpigtails.

As an alternative to forming furcated connector pigtails, separateconnector pigtails can be pre-fabricated and thereafter fusion splicedwith individual fibers from an optical fiber ribbon, and the resultinggroup of fusion spliced regions may be protected in a housing similar tothat employed in a RFK. FIG. 3 illustrates an exemplary cable assembly80 utilizing such a housing 82, with one end of the cable assembly 80including a multi-fiber push-on (MPO) connector 84 affixed to amulti-fiber cable 86 (incorporating a ribbon therein). The multi-fibercable 86 enters one side of the housing 82, and multiple (e.g., twelve)connector pigtails 88 enter the other side of the housing 82. Eachconnector pigtail 88 includes one or more optical fibers 90 terminatedwith a separate connector 92. An advantage of using single fibersplicing compared to the direct furcation process is that furcationtubes may be omitted, thereby saving material and labor costs. Loosetube furcation and termination is also prone to micro bend loss atextreme temperature environments. Furthermore, the processes ofterminating and testing connectors on complex cable assemblies are morechallenging than comparable processes applicable to simple jumpers orpigtails. The small amount of insertion loss introduced by fusionsplicing is more than offset by improved environmental performance andhigher connector quality inherent to pre-fabricated connector pigtails.

As can be appreciated, the term “connector pigtail” is used in thisdisclosure in a generic sense to refer to an optical fiber terminatedwith a fiber optic connector. The optical fiber may be a bare fiber,coated fiber, or buffered fiber (loose or tight buffered), although thelatter two typically include a bare fiber section (e.g., formed byremoving coating(s)) on each end. One end includes a bare fiber sectionfor connectorization/connectivity purposes, while the other end includesa bare fiber section to facilitate fusion splicing.

Optical fiber fusion splicing is the process by which a permanent,low-loss, high-strength, fused (or welded) joint is formed between twooptical fibers. The ultimate goal of optical fiber fusion splicing is tocreate a joint with no optical loss, yet with mechanical strength andlong-term reliability that matches an unspliced continuous fiber. Anexemplary fusion splice subassembly 94 for protecting a splice joint 96formed between bare sections 14A, 14B of two coated optical fibers 10A,10B is schematically illustrated in FIG. 4. After a coating is strippedto expose glass cladding and form the bare sections 14A, 14B, flat fiberend faces are formed, typically by cleaving the exposed glass portionsof the fibers. Then the bare sections 14A, 14B are laterally aligned toeach other, and the fiber tips are heated to their softening point whilebeing pressed together, resulting in formation of a welded splice joint96. Checks such as loss estimation and proof testing (to ensure longterm mechanical reliability) may be performed. The completed splice mustalso be protected from the environment. Packaging 98 for the splicejoint 96 and the bare sections 14A, 14B may include a heat shrinkprotection sleeve or a multi-part housing (optionally containing epoxyor another encapsulating material). If the packaging 98 is provided inthe form of a heat shrink protection sleeve (e.g., including an outerheat shrink member and an inner thermoplastic melt flow adhesive tube),then the heat shrink protection sleeve may include a strength membersuch as a stainless steel rod to serve as a splint to prevent bending ofthe splice joint.

While single-fiber fusion splicing is considerably simpler than a loosetube furcation process, splicing fibers one at a time is still atime-consuming process that requires fiber management during and aftersplicing. The resulting fiber splices are typically packaged in aRFK-style housing. An alternative to single fiber splicing is to usefusion splice-on connectors or mechanical splice connectors on the endsof furcated fibers. The splice point in a splice-on connector isprotected inside one of the connector components, thus eliminating theneed for a separate housing to manage multiple splice joints. Whether inthe context of connector pigtails or splice-on connectors, however,splicing fibers one at a time is very time-consuming, which limitsscalability and concomitantly increases labor and tool utilization.

In view of the foregoing, need exists in the art for improvedribbon-type optical fiber fan-out assemblies and fiber optic cableassemblies incorporating such fan-out assemblies, as well as methods forproducing the same, to address limitations associated with conventionalassemblies and fabrication methods.

SUMMARY

Aspects of the present disclosure provide an optical fiber fan-outassembly with a polymeric material encapsulating a plurality of opticalfibers arranged in a one-dimensional array in a variable fiber pitchtransition segment, a fiber optic cable assembly incorporating such afan-out assembly, and a method for fabricating a multi-fiber assemblyproviding fan-out functionality. In exemplary aspects, a variable pitchtransition segment (also referred to simply as “transition segment”)arranged between a larger pitch first segment and a smaller pitch secondsegment is encapsulated with polymeric material. A plurality of opticalfiber legs terminated with fiber optic connectors extend from an end ofthe first segment, and in the second segment a plurality of opticalfibers extend beyond a boundary of the polymeric material. The polymericencapsulating material may be flexible and low-profile in character, mayconform to a shape of the transition segment, and dispenses with theneed for a housing or other strength member. Optical fibers extendingbeyond a boundary of the polymeric material are subject to being massfusion spliced to another group of multiple optical fibers, and thefusion splices encapsulated with polymeric material, to form a fiberoptic cable assembly. Additional exemplary aspects relate to methods forfabricating multi-fiber assemblies providing fan-out functionality.

In one embodiment of the disclosure, an optical fiber fan-out assemblyis provided. The optical fiber fan-out assembly comprises a plurality ofoptical fibers arranged in a one-dimensional array extending through afirst segment, a second segment, and a transition segment disposedbetween the first and second segments. The optical fiber fan-outassembly further comprises a plurality of optical fiber legs extendingfrom the one-dimensional array at an end of the first segment. Eachoptical fiber leg of the plurality of optical fiber legs includes atleast one optical fiber of the plurality of optical fibers, and a fiberoptic connector that terminates the at least one optical fiber of theoptical fiber leg. The optical fiber fan-out assembly further comprisesa polymeric material encapsulating the plurality of optical fibers inthe transition segment. In the first segment, the one-dimensional arraycomprises a first pitch between centers of adjacent optical fibers ofthe plurality of optical fibers. In the second segment, theone-dimensional array comprises a second pitch between centers ofadjacent optical fibers of the plurality of optical fibers. In thetransition segment, the one-dimensional array transitions from the firstpitch proximate the first segment to the second pitch proximate thesecond segment. In at least a portion of the second segment that isdistal from the transition segment, the plurality of optical fibersextends beyond a boundary of the polymeric material.

In accordance with another embodiment of the disclosure, a fiber opticcable assembly is provided. The fiber optic cable assembly comprises afirst plurality of optical fibers arranged in a one-dimensional arrayextending through a first segment, a second segment, and a transitionsegment disposed between the first and second segments. Each opticalfiber of the first plurality of optical fibers includes a first bareglass section along an end of the second segment that is distal from thetransition segment. The fiber optic cable assembly further comprises aplurality of optical fiber legs extending from the one-dimensional arrayat an end of the first segment, wherein each optical fiber leg of theplurality of optical fiber legs includes at least one optical fiber ofthe first plurality of optical fibers, and a fiber optic connector thatterminates the at least one optical fiber of the optical fiber leg. Thefiber optic cable assembly further comprises a first polymeric materialencapsulating the first plurality of optical fibers in the transitionsegment. In the first segment, the one-dimensional array comprises afirst pitch between centers of adjacent optical fibers of the pluralityof optical fibers. In the second segment, the one-dimensional arraycomprises a second pitch between centers of adjacent optical fibers ofthe plurality of optical fibers. In the transition segment, theone-dimensional array transitions from the first pitch proximate thefirst segment to the second pitch proximate the second segment. In atleast a portion of the second segment, the plurality of optical fibersextends beyond a boundary of the polymeric material. The fiber opticcable assembly further comprises a second plurality of optical fibersarranged in a one-dimensional array, wherein each optical fiber of thesecond plurality of optical fibers includes a second bare glass section.The fiber optic cable assembly further comprises a plurality of fusionsplices connecting ends of the first bare glass sections to ends of thesecond bare glass sections. The fiber optic cable assembly furthercomprises a second polymeric material encapsulating the plurality offusion splices, the first bare glass sections, and the second bare glasssections.

In accordance with another embodiment of the disclosure, a method forfabricating a multi-fiber assembly providing fan-out functionality isprovided. The method comprises arranging a first segment of a firstplurality of optical fibers in a one-dimensional array having a firstpitch between centers of adjacent optical fibers of the first pluralityof optical fibers. A plurality of optical fiber legs extend from theone-dimensional array at an end of the first segment, each optical fiberleg of the plurality of optical fiber legs includes at least one opticalfiber of the first plurality of optical fibers, and a fiber opticconnector that terminates the at least one optical fiber of the opticalfiber leg. The method further comprises arranging a second segment ofthe first plurality of optical fibers in a one-dimensional array havinga second pitch between centers of adjacent optical fibers of the firstplurality of optical fibers. The second pitch is smaller than the firstpitch. The arranging of the first segment and the second segmentincludes defining a transition segment between the first and secondsegments, and in the transition segment the one-dimensional arraytransitions from the first pitch proximate the first segment to thesecond pitch proximate the second segment. The method further comprisesencapsulating the first plurality of optical fibers at least in thetransition segment with a polymeric material. In at least a portion ofthe second segment, the first plurality of optical fibers extends beyonda boundary of the polymeric material.

In accordance with another embodiment of the disclosure, an opticalfiber assembly formed by multiple steps is provided. One step comprisesarranging a first segment of a first plurality of optical fibers in aone-dimensional array having a first pitch between centers of adjacentoptical fibers of the first plurality of optical fibers, wherein aplurality of optical fiber legs extend from the one-dimensional array atan end of the first segment, each optical fiber leg of the plurality ofoptical fiber legs includes at least one optical fiber of the firstplurality of optical fibers and a fiber optic connector that terminatesthe at least one optical fiber of the optical fiber leg. Another stepcomprises arranging a second segment of the first plurality of opticalfibers in a one-dimensional array having a second pitch between centersof adjacent optical fibers of the first plurality of optical fibers, andthe second pitch is smaller than the first pitch, wherein the arrangingof the first segment and the second segment includes defining atransition segment between the first and second segments, and in thetransition segment the one-dimensional array transitions from the firstpitch proximate the first segment to the second pitch proximate thesecond segment. Another step comprises encapsulating the first pluralityof optical fibers at least in the transition segment with a polymericmaterial. In at least a portion of the second segment, the firstplurality of optical fibers extends beyond a boundary of the polymericmaterial.

Additional features and advantages will be set forth in the detaileddescription which follows, and in part will be readily apparent to thoseskilled in the technical field of optical connectivity. It is to beunderstood that the foregoing general description, the followingdetailed description, and the accompanying drawings are merely exemplaryand intended to provide an overview or framework to understand thenature and character of the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings are included to provide a furtherunderstanding, and are incorporated in and constitute a part of thisspecification. The drawings illustrate one or more embodiment(s), andtogether with the description serve to explain principles and operationof the various embodiments. Features and attributes associated with anyof the embodiments shown or described may be applied to otherembodiments shown, described, or appreciated based on this disclosure.

FIG. 1 is a cross-sectional view of a conventional coated optical fiber,prior to stripping of a multi-layer polymer coating from glass cladding.

FIG. 2 is a exploded (i.e., unassembled) perspective view of aconventional ribbon fan-out kit suitable for separating fibers of anoptical fiber ribbon into multiple fibers individually encased withinfurcation tubes.

FIG. 3 is a top plan view of a conventional cable assembly utilizing ahousing protecting fusion splices between separate connector pigtailsand a multi-fiber cable terminated with a MPO connector.

FIG. 4 is a schematic cross-sectional view of a fusion splicesubassembly for protecting a splice joint between bare sections of twocoated optical fibers, with the bare sections being formable bystripping of a coating therefrom.

FIG. 5 is a perspective view of a portion of an optical fiber fan-outassembly according to one embodiment, including first, second, andtransition segments, a bundling body encapsulating buffered sections ofa plurality of optical fibers in the first segment, and a continuouspolymeric material encapsulating unbuffered sections of the plurality ofoptical fibers in the transition and second segments.

FIG. 6 is a perspective view of a portion of an optical fiber cableassembly incorporating an optical fiber fan-out assembly according toFIG. 5, following fusion splicing of optical fibers of the fan-outassembly to optical fibers of a ribbon cable and overcoating of thesplice region.

FIG. 7 is a perspective view of a portion of the optical fiber fan-outassembly of FIG. 5 during one step in the fabrication thereof, showingtwelve connector pigtails held together at a first pitch by a bundlingbody to form a first segment, prior to formation of a transitionsegment.

FIG. 8 is a perspective view of a portion of the optical fiber fan-outassembly of FIG. 5 during another step in the fabrication thereof,showing a section of unbuffered optical fibers received within a fibersorting fixture to set a second pitch, and to form the shape of atransition segment prior to encapsulation of the transition segment.

FIG. 9 is a top plan view of a portion of the optical fiber fan-outassembly of FIG. 5 during a step in the fabrication thereof, followingformation of the shape of the transition segment prior to encapsulationthereof, showing the shape of bends of the optical fibers in thetransition segment.

FIG. 10 is a perspective view of a portion of the optical fiber fan-outassembly of FIG. 5 during a step in the fabrication thereof, followingformation of a holding body to encapsulate the plurality of opticalfibers along an interface between the second segment and the transitionsegment to set positions of optical fibers in the transition segmentprior to encapsulation thereof.

FIG. 11 is a perspective view of a portion of the optical fiber fan-outassembly of FIG. 5, following encapsulation of the transition segmentand a portion of the second segment.

FIG. 12A is an upper perspective view illustration of a bare fusionspliced section of two optical fiber ribbon segments forming a splicedribbon cable, with a first lateral edge portion of the spliced ribboncable submerged in a pool of molten thermoplastic material atop asubstantially level, flat heated surface, and with the ribbon cablebeing tilted at an approximately forty-five degree angle during a ribboncable insertion step, such that a second lateral edge portion of thespliced ribbon cable is arranged at a level above the first lateral edgeportion.

FIG. 12B illustrates the items of FIG. 12A, with the entire fusionspliced section of the spliced ribbon cable disposed in the pool ofmolten thermoplastic material atop the substantially level, flat heatedsurface, and with the first lateral edge portion being arranged atsubstantially the same horizontal level as the second lateral edgeportion of the spliced ribbon cable.

FIG. 13 is a top plan view of the optical fiber fan-out assembly of FIG.5 including the twelve connector pigtails extending from the firstsegment, polymeric material encapsulating the transition segment and aportion of the second segment, and stripped and cleaved optical fibersextending beyond the polymeric material of the second segment.

FIG. 14 is a top plan view of the optical fiber fan-out assembly of FIG.13, with the second segment retained by a fiber holding jig of a massfusion splicing apparatus to prepare the optical fiber fan-out assemblyfor mass fusion splicing.

FIG. 15 is a perspective view of a fiber optic cable assemblyincorporating the optical fiber fan-out assembly of FIG. 13, followingsplicing of the optical fiber fan-out assembly to an optical fiberribbon pre-terminated with a MPO connector.

FIG. 16A is a perspective view of a fiber arrangement including aplurality of optical fibers extending through a larger pitch firstsegment, a smaller pitch second segment, and a transition segment allbeing useable for forming an optical fiber fan-out assembly according toone embodiment, with the plurality of optical fibers arranged in amulti-dimensional (3×4) array in the first segment, and arranged in aone-dimensional (1×12) array in the second segment.

FIG. 16B is a side elevation view of the plurality of optical fibers ofFIG. 16A.

FIG. 16C is a side elevation view of the plurality of optical fibers ofFIG. 16B with a continuous polymeric material encapsulating theplurality of optical fibers in the transition segment, in a portion ofthe first segment, and in a portion of the second segment.

FIG. 17A is a perspective view of a plurality of optical fibersextending through a larger pitch first segment, a smaller pitch secondsegment, and a transition segment all being useable for forming anoptical fiber fan-out assembly according to one embodiment, with theplurality of optical fibers arranged in a hexagonally packed cylindricalarray in the first segment, and arranged in a one-dimensional (lx 12)array in the second segment.

FIG. 17B is a side elevation view of the plurality of optical fibers ofFIG. 17A.

FIG. 17C is a side elevation view of the plurality of optical fibers ofFIG. 17B with a continuous polymeric material encapsulating theplurality of optical fibers in the transition segment, in a portion ofthe first segment, and in a portion of the second segment.

DETAILED DESCRIPTION

Various embodiments will be further clarified by examples in thedescription below. In general, the description relates to an opticalfiber fan-out assembly with a polymeric material encapsulating aplurality of optical fibers arranged in an array in a variable fiberpitch transition segment, a fiber optic cable assembly incorporatingsuch a fan-out assembly, and a method for fabricating a multi-fiberassembly that provides fan-out functionality. The variable pitchtransition segment is arranged between a larger pitch first segment(e.g., having a 900 μm or 950 μm pitch corresponding to tight bufferedoptical fibers) and a smaller pitch second segment (e.g., having a 250μm or 200 μm pitch corresponding to coated optical fibers). Thetransition segment as well as at least a portion of second segment areencapsulated with polymeric material. Multiple unbuffered optical fibersof the second segment may extend beyond the polymeric material to enablesuch optical fibers to be spliced. In the second segment, theinter-fiber pitch may match that of a conventional optical fiber ribbon,thereby permitting the use of efficient mass fusion splicing between theoptical fiber fan-out assembly and an optical fiber ribbon (which mayhave been previously terminated an opposing end with a multi-fiberconnector). Thereafter, the splice region and any previously uncoveredfibers are encapsulated with polymeric material.

Such an optical fiber fan-out assembly and corresponding optical fibercable assembly may dispense with a separate housing or strength memberin transition regions (as well as in splice regions), and furtherdispense with the labor and expense associated with the use of furcationtubes. Migrating from complex fan-out assemblies to fan-outsubassemblies with mass fusion splicing interfaces presents significantmanufacturing and cost advantages compared to conventional furcationprocesses and reliance on single fiber fusion splicing. Production ofoptical fiber fan-out assemblies and corresponding optical fiber cableassemblies may be fully automated, without requiring the labor-intensivefurcation process. Optical fiber fan-out assemblies and correspondingoptical fiber cable assemblies disclosed herein may also exhibit levelsof mechanical flexibility not previously achievable with assembliespreviously relying on rigid furcation bodies/housings or other strengthmembers.

FIG. 5 is a perspective view of a central portion of an optical fiberfan-out assembly 100 according to one embodiment, including a firstsegment 102, a second segment 104, and a transition segment 106 arrangedbetween the first and second segments 102, 104. A plurality of opticalfibers 108 extends through, and forms a one-dimensional array in, eachof the foregoing segments 102, 104, 106. In the first segment 102, theone-dimensional array of optical fibers 108 has a first pitch betweencenters of adjacent optical fibers 108, and in the second segment, theone-dimensional array of optical fibers 108 has a second pitch betweencenters of adjacent optical fibers 108, with the second pitch beingsmaller than the first pitch. A larger boundary 110 of the transitionsegment 106 has the first pitch, a smaller boundary of 112 of thetransition segment 106 has the second pitch, and an interior of thetransition segment 106 has a pitch that varies between the first pitchand the second pitch. The first pitch is larger (e.g., 900 μm) toaccommodate tight buffer material (or jacket material and/or othertubular material) present on the optical fibers 108 in the first segment102. Thus, the optical fibers 108 in the first segment 102 comprisebuffered optical fibers.

A bundling body 114 encapsulates optical fibers 108 (and associatedtight buffer or jacket material) over at least a portion of the firstsegment 102. Although FIG. 5 shows the bundling body 114 as beingcoextensive with the first segment 102, in certain embodiments thebundling body 114 may be confined to a portion of the first segment 102,or possibly omitted. Multiple optical fiber legs 116 extending from thebundling body 114 include one or more buffered (e.g., tight buffered)optical fibers of the plurality of optical fibers 108 and separate fiberoptic connectors (not shown), which may embody simplex or duplexconnectors, for terminating the buffered optical fibers. In thetransition segment 106 and the second segment 104, the optical fibers108 are devoid of buffer material (i.e., are unbuffered), enablingattainment of a smaller pitch (e.g., 250 μm or 200 μm) between adjacentoptical fibers 108. A polymeric material 118 encapsulates optical fibers108 in the transition segment 106 and in the second segment 104. Thepolymeric material 118 may be arranged in contact with the bundling body114. In a portion of the second segment 104, the plurality of opticalfibers 108 includes an uncovered section 122 that extends beyond aboundary 120 of the polymeric material 118. The presence of opticalfibers 108 extending beyond the polymeric material 118 renders themavailable to be fusion spliced with another group of optical fibers(e.g., from an optical fiber ribbon), preferably via a mass fusionsplicing process. In certain embodiments, the uncovered section 122 ofoptical fibers 108 extending beyond the boundary 120 of the polymericmaterial 118 may embody uncoated (bare glass) optical fibers.

The polymeric material 118 and the bundling body 114 (as well as aholding body, which will be described hereinafter in connection withFIG. 10) may each be generically described herein as an overcoatingmaterial. Overcoating materials may be formed by any suitable processsuch as molding (including but not limited to injection molding) orcoating (e.g. dip coating, spray coating, or the like). Desiredovercoating materials should be water-resistant, since moisture is knownto chemically interact with the glass cladding of optical fibers andcause expansion of micro defects in the glass, thereby leading tolong-term failure of optical fibers. Desired overcoating materials alsomay be free of sharp particles (e.g., inorganic filler particles) andair bubbles.

In certain embodiments, overcoating materials are applied by contactinga desired portion of an optical fiber fan-out assembly (e.g., includingat least a transition segment thereof) with molten material, and thenallowing the molten material to cool and solidify aroundfiber-containing portions of the optical fiber fan-out assembly. If amold is used, then molten material may be supplied to the interior of amold and then cooled and solidified, followed by removal of thesolidified material from the mold. If a dip coating process is used,then a desired portion of an optical fiber fan-out assembly may bedipped into a heated pool of molten material, followed by removal of theoptical fiber fan-out assembly portion to be cooled by an air or othergaseous environment, optionally aided by gas circulation.

In certain embodiments, one or more overcoating materials may includesolid thermoplastic materials such as polyamide, polyolefin, apolyamide-polyolefin copolymer, a polyamide grafted polyolefin, and acopolyester. In certain embodiments, one or more coating materials maycomprise a melt-flow thermoplastic adhesive material. Otherthermoplastic materials as well as other polymeric non-thermoplasticmaterials may be used. To avoid thermal degradation of one or morecoating layers of pre-coated sections of optical fibers, molten material(e.g., molten thermoplastic) used for overcoating materials should bemaintained at a processing temperature below a melt temperature of theone or more coating layers. In certain embodiments, an overcoatingmaterial may comprise a UV-curable material; alternatively, anovercoating may be devoid of UV-curable components.

If an overcoating material includes a thermoplastic, in certainembodiments, molten thermoplastic material may also be maintained at aprocessing temperature at which the molten thermoplastic material has amelt viscosity in a range of from about 100 centipoises (cps) to about10,000 cps, or more preferably in a subrange of from about 1000 cps toabout 10,000 cps, or more preferably in a subrange of from about 2000cps to about 4000 cps. A desired thermoplastic material should also bechemically stable at the processing temperature, have a glass transitiontemperature of no greater than −40° C., have a service temperaturespanning at least a range of from −40° C. to 85° C. without sufferingsignificant mechanical and/or optical performance degradation, exhibitstrong adhesion to fiber coating layers and bare glass, be free fromcharring, and/or exhibit minimal to no outgassing (e.g., of volatileorganic compounds and/or other constituents). A glass transitiontemperature is the point at which a material goes from a hard brittlestate to a flexible or soft rubbery state as temperature is increased. Acommon method for determining glass transition temperature uses theenergy release on heating in differential scanning calorimetry. If aplastic (e.g., thermoplastic) material associated with an optical fiberis exposed to a temperature below its glass transition temperature, thematerial will become very hard, and the optical fiber may be susceptibleto micro bend losses. In certain embodiments, service temperature of anovercoating material may be determined by compliance with one or moreindustry standards for telecommunication fiber reliability testing, suchas (but not limited to): ITU-T G.652, IED60793-2, Telcordia GR-20-CORE,and TIA/EIA-492. A desirable overcoating material is preferably notsubject to delamination during normal handling over the required serviceconditions and lifetime of an optical fiber assembly.

In certain embodiments, overcoating material present over at least aportion of an optical fiber fan-out assembly (including but not limitedto a transition segment) is conformally coated over optical fibersarranged in a one-dimensional array, with a narrow width profile and arelatively low thickness profile relative to optical fibers containedtherein. Together with mechanical properties of the overcoatingmaterial, providing the overcoating material with narrow width and lowthickness profiles serves to enhance mechanical flexibility of theoptical fiber fan-out assembly.

With continued reference to FIG. 5, the plurality of optical fibers 108is arranged in a one-dimensional array (albeit with different pitch incertain regions), with the one-dimensional array having a lengthwiseaxis L, a widthwise axis W orthogonal to the lengthwise axis L, and athickness axis T orthogonal to the lengthwise axis L and the widthwiseaxis W. In certain embodiments, the polymeric material 118 encapsulatingthe plurality of optical fibers 108 in the transition segment 106 has anarrow width profile, with a width along the widthwise axis W that ispreferably no greater than 3 mm (or no greater than 2 mm, or no greaterthan 1 mm, or no greater than 0.75 mm, or no greater than 0.5 mm) widerat any position than a widthwise extent of the plurality of opticalfibers 108 in the transition segment 106. In certain embodiments, thepolymeric material 118 encapsulating the plurality of optical fibers 108in the transition segment 106 has a low thickness profile, with athickness along the thickness axis T that is preferably no greater than3 mm (or no greater than 2 mm, or no greater than 1 mm, or no greaterthan 0.75 mm, or no greater than 0.5 mm) thicker than a thickness of theplurality of optical fibers in the transition segment 106. Presence ofthe polymeric material 118 encapsulating the plurality of optical fibers108 dispenses with the need for an RFK-style housing.

As noted previously, the presence of overcoating material with a narrowwidth profile, a low thickness profiles, and suitable mechanicalproperties permits an optical fiber fan-out assembly to exhibit a highdegree of flexibility. In certain embodiments, optical fibers 108extending beyond a boundary 120 of the polymeric material 118 may befusion spliced to an optical fiber ribbon 138 (e.g., incorporating thesecond plurality of optical fibers 132 shown in FIG. 6), and flexibilityof at least portions of the optical fiber fan-out assembly may besufficiently high to permit comparison to the flexibility of the opticalfiber ribbon. For example, in certain embodiments, one or more of thetransition segment 106, the first segment 102, or the second segment 104may be at least 30% as flexible (or at least 40% as flexible, or atleast 50% as flexible, or at least 60% as flexible, or at least 70% asflexible) as the optical fiber ribbon in bending about the widthwiseaxis W or the thickness axis T.

In certain embodiments, the polymeric material 118 in the transitionsegment 106 is conformally coated over the plurality of optical fibers108, such that a shape of the polymeric material 118 closely follows anouter boundary of an array formed by the plurality of optical fibers108. In certain embodiments, in at least a portion of the transitionsegment 106 proximate the second segment 104 the array of optical fibers108 comprises a one-dimensional array, and outermost optical fibers 108of the in the transition segment 106 embody S-bends (i.e., correspondingto half a period of a cosine function) without abrupt changes indirection. Moreover, in certain embodiments, the polymeric materialencapsulating the plurality of optical fibers 108 in the transitionsegment 106 is provided in a similar shape without abrupt (e.g.,stepwise) changes in width. In certain embodiments, a first widthwisedimension corresponding to a maximum widthwise extent of theone-dimensional array varies with position along a lengthwise dimensionof the transition segment 106, and a second widthwise dimensioncorresponding to a maximum widthwise extent of the polymeric material118 varies with position along the lengthwise dimension of thetransition segment 106. In such embodiments, the second widthwisedimension exceeds the first widthwise dimension at each position by awidth differential, and the width differential varies with position byno more than about 30% (or by no more than about 20%, or by no more thanabout 15%, or by no more than about 10%, or by no more than about 5%)along the lengthwise dimension of the transition segment 106. Restated,in such an instance, the width of the polymeric material 118 generallyfollows a width of a plurality of optical fibers 108 encapsulatedtherein.

As shown in FIG. 6, the optical fiber fan-out assembly 100 is devoid ofa housing and devoid of a strength member arranged in, on, or around thepolymeric material 118 encapsulating the plurality of optical fibers 108in the transition segment 106.

FIG. 6 is a perspective view of a portion of an optical fiber cableassembly 130 incorporating an optical fiber fan-out assembly asdescribed previously herein in connection to FIG. 5. Elements of FIG. 6corresponding exactly to FIG. 5 will not be described again for sake ofbrevity. The optical fiber cable assembly 130 incorporates theabove-described optical fiber fan-out assembly 100 following: (A) fusionsplicing of the plurality optical fibers 108 (i.e., a “first” pluralityof optical fibers) of the optical fan-out assembly 100 to a plurality ofoptical fibers 132 (i.e., a “second” plurality of optical fibers) of theoptical fiber ribbon 138, and (B) overcoating of a fusion splice region134 as well as previously uncovered or bare (e.g., previously stripped)sections of optical fibers (e.g., uncovered section 122 of the pluralityof optical fibers 108 shown in FIG. 5) with a second polymeric material140. Preferably, a portion of the second polymeric material 140 extendsover the boundary 120 of the (first) polymeric material 118, to ensureformation of a continuous barrier over the (first) plurality of opticalfibers 108. Optionally, an extension portion of the second polymericmaterial 136 may also extend over an unstripped section of the opticalfiber ribbon 138, to provide for a continuous barrier over any stripped(i.e., bare) portions of the second plurality of optical fibers 132.Essentially, presence of the polymeric material 118 and the secondpolymeric material 140 in a coating that substantially conforms to aperimeter of the (first) plurality of optical fibers 108 and the secondplurality of optical fibers 132 serves to “ribbonize” the plurality ofoptical fibers 108, 132. In certain embodiments, the second polymericmaterial 136 may be compositionally the same as the polymeric material118 covering the first, second, and transition segments 102, 104, 106;in other embodiments, the polymeric material 118 and the secondpolymeric material 1136 may be compositionally different. Compositionaldetails and exemplary application methods for the second polymericmaterial 140 may be the same as previously described in connection withthe polymeric material 118 of FIG. 5. As shown, the optical fiber cableassembly 130 is devoid of any housing or strength member arranged in,on, or around (i) the polymeric material 118 encapsulating the firstplurality of optical fibers (at least) in the transition segment, and(ii) the second polymeric material 136 encapsulating the fusion spliceregion 134 as well as previously stripped (bare) glass sections of the(first) plurality of optical fibers 108 and the second plurality ofoptical fibers 132. It is to be appreciated that a distal end of theoptical fiber ribbon 138 (which opposes the previously stripped (bare)glass sections of the second plurality of optical fibers 132 terminatingat the splice region 134) may be terminated with a multi-fiber connector(not shown, but as depicted in FIG. 15), such as a MPO connector or aconnector any other suitable type.

FIG. 7 is a perspective view of a portion of the optical fiber fan-outassembly 100 of FIG. 5 during one step in the fabrication thereof,showing tight buffered optical fiber legs 116 formed from twelvepre-fabricated connector pigtails (each including a fiber opticconnector terminating at least one tight optical fiber) being heldtogether by a bundling body 114 to form a first segment 102, prior toformation of a transition segment. For each optical fiber leg 116, adesired length (e.g., about 8 cm) may be initially removed inpreparation for formation of the bundling body 113. In certainembodiments, different optical fiber legs 116 may have differentlengths. As illustrated, the first segment 102 includes a plurality ofoptical fibers 108 having a first pitch (e.g., 900 μm), with the firstpitch between adjacent fibers of the plurality of optical fibers 108being the same beyond either end of the bundling body 114. The bundlingbody 114 may be formed by any suitable process and using any suitablematerial described previously herein in connection with overcoatingmaterials. In certain embodiments, the bundling body 114 may be formedby a melt flow thermoplastic adhesive material using a process such asdip coating or molding. The purpose of the bundling body 114 is to holdthe plurality of optical fibers 108 in a fixed one-dimensional array topermit subsequent formation of a transition segment, as shown in FIGS. 8and 9.

FIG. 8 is a perspective view of a portion of the optical fiber fan-outassembly 100 of FIG. 5 during another step in the fabrication thereof,showing a section of the plurality of optical fibers 108 received withina fiber sorting fixture 144 to set a second pitch, and to form the shapeof a transition segment 106 prior to encapsulation of the transitionsegment 106 with polymeric material. Starting at left, for the opticallegs 116 held together by the bundling body 114, tight buffers 142surrounding the optical fibers 108 are visible, having been maintainedintact during formation of the bundling body 114. Each optical leg 116is devoid of a furcation tube. Within the bundling body 114, the tightbuffers 142 and optical fibers 108 are kept straight and parallel,configured as a one-dimensional array with a constant pitch betweenadjacent optical fibers 108. The fiber sorting fixture 144 includes aslot 146 having at least one opening dimension (e.g., height) thatclosely matches a corresponding dimension of unbuffered sections ofoptical fibers 108. Such optical fibers 108 may be coated, providing anouter diameter of about 250 μm or about 200 μm. The optical fibers 108may initially be fed into the slot 146 at a position close to thebundling body 114, where positions of individual optical fibers 108 arediscernable and well-defined without crossover. The fiber sortingfixture 144 may then be moved away from the bundling body 114 to adesignated distance to form the transition segment 106. Within the slot146, the optical fibers may be closely packed by lateral compressionapplied by a shim 148. The optical fibers 108 are held within the fibersorting fixture 144 at a second pitch (e.g., 250 μm or 200 μm) that issmaller than the first pitch maintained by the bundling body 114, andthe second pitch may be maintained for optical fibers exiting the fibersorting fixture 144.

FIG. 9 is a top plan view of a portion of the optical fiber fan-outassembly 100 of FIG. 5 during a step in the fabrication thereof,following formation of the shape of the transition segment 106 prior toencapsulation thereof, showing the shape of bends of the optical fibers108 in the transition segment 106. As shown, the outermost opticalfibers 150, 152 in the transition segment 106 experience the tightestbend radius. The shape of the transition segment 106 in certainembodiments is designed to maximize the bend radius along the path. Incertain embodiments, the path of at least the outermost optical fibers150, 152 in the transition segment 106 is shaped corresponding to a halfperiod of a cosine function, which is also known as an S-bend in thefield of optical waveguide design. For example, for a 12 fiber fan-outthe outermost fiber has a lateral position y as a function oflongitudinal position x:

${y = {\frac{5.5\left( {P_{1} - P_{2}} \right)}{2}{\cos\left( \frac{\pi\; x}{L} \right)}}},$where P₁ is the first (larger) fiber pitch, P₂ is the second (smaller)fiber pitch, and L is the length of the transition segment. Thepreferred transition length is about 20 mm, so that the minimum bendradius, which occurs at both ends of the transition, is at least 22.7mm. This bend radius does not present any bend loss for standard singlemode fibers. When considering out-of-plane flexing of the transitionsegment 102, the effective bend radius which includes in-plane andout-of-plane bends is reduced. For example, if the out-of-plane bendradius is 25 mm, the effective bend radius is reduced to 16.8 mm, forwhich the macro bend loss for Corning® SMF-28® Ultra fiber (commerciallyavailable from Corning, Inc., Corning, N.Y.) is still less than 0.01 dBat for transmission of 1625 nm. Thus, in certain embodiments, eachS-bend formed in the transition segment 106 preferably includes aminimum bend radius of at least 22.7 mm.

FIG. 10 is a perspective view of a portion of the optical fiber fan-outassembly 100 of FIG. 5 during a step in the fabrication thereof,following formation of a holding body 156 to encapsulate the pluralityof optical fibers 108 along an interface between the second segment 104and the transition segment 106, to set positions of the optical fibers108 of the transition segment 106 prior to encapsulation thereof. Theholding body 156 may be formed proximate to a position where the opticalfibers 108 were held by the fiber sorting fixture 144 (shown in FIG. 8).In certain embodiments, the holding body 156 can be formed while theoptical fibers 108 are retained by the fiber sorting fixture 144, andfollowing formation of the holding body 156, the fiber sorting fixture144 may be removed. The holding body 156 may be formed by any suitableprocess and using any suitable material described previously herein inconnection with overcoating materials. In certain embodiments, theholding body 156 may be formed by a melt flow thermoplastic adhesivematerial using a process such as dip coating or molding. In certainembodiments, the holding body 156, the bundling body 114, and asubsequently applied polymeric material 120 (shown in FIG. 11) may becompositionally the same. In other embodiments, one or more of theholding body 156, the bundling body 114, and the polymeric material 120may be compositionally different from the others. In yet otherembodiments, the holding body 156 may be tape or the like.

Following formation of the holding body 156, optical fibers 108 in aremainder of the transition segment 106 as well as any desired length(e.g., some or all) of the second segment 104 may be coated withpolymeric material 120, as shown in FIG. 11. Such polymeric materialpreferably encapsulates at least a portion of the holding body 156. Theresulting optical fiber fan-out assembly includes multiple optical fiberlegs 116 extending from the bundling body 114, as well as optical fibers108 arranged in a first segment 102 having a constant, large fiberpitch, a transition segment 106 having a variable pitch, and a secondsegment 104 having a constant, small fiber pitch. Optical fibers 108 inthe transition segment 106 and at least a portion of the second segment104 are encapsulated with polymeric material 120, which is preferablycontinuous in character. Although FIG. 11 shows the entire secondsegment 104 as being encapsulated with polymeric material 120, it is tobe appreciated that along an end portion of the second segment 104, thepolymeric material 120 and any coating on the optical fibers 108 can bestripped, and ends of the resulting bare optical fibers 108 may becleaved, to prepare the optical fibers 108 to be fusion spliced (e.g.,mass fusion spliced) to fibers of another optical ribbon (not shown).Since optical fibers 108 in the second segment 104 may have the samepitch as optical fibers of a conventional optical fiber ribbon, aconventional mass fusion splicing apparatus may be used to mass fusionsplice the optical fiber fan-out assembly 100 to the other opticalribbon.

In certain embodiments, coated optical fibers subject to being fusionspliced and encapsulated according to methods disclosed herein areprepared for fusion splicing (e.g., by stripping ends thereof) utilizingnon-contact fiber stripping methods and/or apparatuses, such as thosedisclosed in U.S. Pat. No. 9,167,626 (“the '626 patent”), which ishereby incorporated by reference herein. Briefly, the '626 patentdiscloses use of a heater configured for heating a heating region to atemperature above a thermal decomposition temperature of at least onecoating of an optical fiber, a securing mechanism for securelypositioning a lengthwise section of the optical fiber in the heatingregion, and a controller operatively associated with the heater andconfigured to deactivate the heater no later than immediately afterremoval of the at least one coating from the optical fiber. Thermaldecomposition of at least one coating of an optical fiber reduces orminimizes formation of flaws in optical fibers that may be generated bymechanical stripping methods and that can reduce their tensile strength.Following stripping of at least one coating layer from the end sectionsof the optical fibers, the bare glass end sections of the optical fibersmay be fusion spliced using conventional fusion splicing method stepsknown to those skilled in the art. Variations of the techniquesdisclosed in the '626 patent are disclosed in U.S. Patent ApplicationPublication Nos. 2016/0349453 and 2017/0001224, the disclosures of whichare also hereby incorporated by reference herein. Non-contact strippingmethods using lasers or hot gases, as well as mechanical strippingmethods, are also possible in certain embodiments.

FIGS. 12A and 12B illustrate a heating apparatus 164 useable for coatingportions of fusion spliced first and second pluralities of opticalfibers 108, 132 with thermoplastic material, such as during fabricationof a cable assembly incorporating a fan-out assembly. The firstplurality of optical fibers 108 includes a section coated with polymericmaterial 118 as well as an uncovered (e.g., bare glass) section 122, andmay correspond to the optical fiber fan-out assembly 100 of FIG. 5. Thesecond plurality of optical fibers 132 is included in an optical fiberribbon 138 of which a portion is stripped to yield an uncovered (e.g.,bare glass) section 158. A distal end of the optical fiber ribbon 138may be terminated with a multi-fiber connector (not shown). Ends of theuncovered sections 122, 158 are fusion spliced (e.g., mass fusionspliced) at a splice region 134. The heating apparatus 164 includes abody 166 that contains an internal electric cartridge heater 167. A poolof molten thermoplastic material 160 is arranged atop a substantiallylevel, flat heated surface 168. Lateral edges 162A, 162B of the pool ofmolten thermoplastic material 160 extend to lateral edges 170A, 170B ofthe flat heated surface 168 without overflowing, due to lowertemperature at the lateral edges 170A, 170B as well as surface tensionof the molten thermoplastic material 160. As shown in FIG. 12A, theuncovered sections 122, 158 and the splice region 134 are arranged abovethe pool of molten thermoplastic material 160, with the splice joint 134roughly centered above the pool, and with the length of the poolexceeding the combined length of the uncovered sections 122, 158. Asshown, a first side 172A of the fusion spliced first and secondpluralities of optical fibers 108, 132 initially contacts the pool ofmolten thermoplastic material 160, while the second side 126B of thefusion spliced first and second pluralities of optical fibers 108, 132remains elevated above the pool. Thereafter, the remainder of the fusionspliced first and second pluralities of optical fibers 108, 132gradually tilt to a more horizontal orientation and are submerged intothe pool, as shown in FIG. 12B. Such figure shows the uncovered sections122, 158 and the splice region 134 submerged in the pool of moltenthermoplastic material 160. Thereafter, the fusion spliced first andsecond pluralities of optical fibers 108, 132 may be removed from thepool of molten thermoplastic material 160 in substantially a reversemanner from which it was introduced into the pool, and the molten liquidmay be cooled to yield a solid thermoplastic overcoating that extendsover the previously uncovered sections 122, 158 and the splice region134. In certain embodiments, the solid thermoplastic overcoating maycomprise a melt-flow thermoplastic adhesive material, such asTECHNOMELT® PA 6208 polyamide material (Henkel Corp., Dusseldorf,Germany).

Further details regarding thermoplastic overcoating of fusion splicedoptical fibers and/or portions of fiber optic cable assemblies aredisclosed in International Application No. PCT/US2018/021685 filed onMar. 9, 2018, wherein the content of the foregoing application is herebyincorporated by reference.

FIG. 13 is a top plan view of an optical fiber fan-out assembly 100Aaccording to one embodiment, including a single group 180 of twelveoptical fiber legs 116 at one end, and twelve stripped and cleaved bareglass optical fibers 108 exposed as part of an uncovered section 122 atan opposite end. Each optical fiber leg 180 is terminated with aseparate fiber optic connector 182. Although a simplex connector 182 isshown, in alternative embodiments each optical fiber leg 116 may includetwo optical fibers 108 and be terminated with a duplex connector. Incertain embodiments, each optical fiber leg 116 is terminated with afiber optic connector selected from the group consisting of: simplex SCconnectors, simplex LC connectors, duplex SC connectors, and duplex LCconnectors. Although FIG. 13 illustrates a single group 180 ofsubstantially identical optical fiber legs 116, in certain embodimentsmultiple groups of optical fiber legs having different characteristics(e.g., different lengths, different connectors, etc.) may be provided ina single optical fiber fan-out assembly. Moreover, although twelveoptical fiber legs 116 are illustrated, it is to be appreciated that anydesired number of optical fibers and optical fiber legs may be employedin optical fiber fan-out assemblies (and corresponding cable assemblies)as disclosed herein.

With continued reference to FIG. 13, the optical fiber legs 116 extendfrom a constant width (and larger fiber pitch) first segment 102, with avariable width (and variable fiber pitch) transition segment 106arranged between the first segment 102 and a constant width (and smallerfiber pitch) second segment 104. Polymeric material 118 encapsulates thetransition segment 106, a portion of the second segment 104, and thefirst segment 102. An uncovered section 122 of the second segment 104includes portions of the plurality of optical fibers 108 extendingbeyond the polymeric material 118. Such optical fibers 108 extendingbeyond the polymeric material 118 in the uncovered section 122 mayoptionally be stripped (bare glass) and cleaved, and are available forfusion splicing.

FIG. 14 is a top plan view of the optical fiber fan-out assembly 100A ofFIG. 13, with the second segment 104 retained by a fiber holding jig 190of a conventional mass fusion splicing apparatus (not shown) to preparethe optical fiber fan-out assembly 100A for mass fusion splicing to anoptical fiber ribbon (not shown), which may be held by anotherconventional fiber holding jig. An example of a suitable mass fusionsplicer may include a Sumitomo Type-66M12 mass fusion splicer (SumitomoElectric Industries, Ltd., Tokyo, Japan). Elements of FIG. 14corresponding exactly to FIG. 13 will not be described again for sake ofbrevity.

FIG. 15 is a perspective view of one embodiment of a fiber optic cableassembly 130A incorporating the optical fiber fan-out assembly 100A ofFIG. 13, following splicing of the optical fiber fan-out assembly to anoptical fiber ribbon 186 that is pre-terminated with a MPO connector188, and following encapsulation of the splice region 134 with a secondpolymeric material 140 (e.g., as described previously in connection withFIG. 6). A first polymeric material 120 may encapsulate the transitionsegment 106, at least a portion of the second segment 104, andoptionally at least a portion of the first segment 102. Following massfusion splicing between bare fiber (e.g., previously uncovered orpreviously stripped) sections of the second segment 104 and the opticalfiber ribbon 186 to form the splice region 134, the bare fiber sectionsas well as the splice region are encapsulated with the second polymericmaterial 140. Preferably, the second polymeric material 140 overlaps atleast a portion of the first polymeric material 120 to providecontinuous protection over a section extending from the MPO connector188 to the first segment 102. Although a MPO connector is illustrated inFIG. 15, it is to be appreciated that the connector 188 may embody anysuitable type of multi-fiber connector.

Current mass fusion splicing technology permits fusion splicing of twogroups of optical fibers each arranged in a one-dimensional array (i.e.,a linear array). In certain embodiments, a plurality of optical fibersextend through a first segment, a second segment, and a transitionsegment disposed between the first and second segments, wherein: (i) inat least a portion of the first segment, the plurality of optical fibersare arranged in a multi-dimensional array or other multi-dimensionalconfiguration, and (ii) in at least a portion of the second segment, theplurality of optical fibers are arranged in a one-dimensional array.Such embodiments still permit distal ends of optical fibers of thesecond segment to be aligned and fusion spliced with ends of opticalfibers of an optical fiber ribbon using a mass fusion splicingapparatus. The term “multi-dimensional configuration” in this contactsrefers to an arrangement in which multiple fibers are arranged in athree-dimensional manner within a jacket or other tubular material;i.e., an arrangement other than a one-dimensional array. And the term“multi-dimensional array” in this context may include a regularlyordered array (e.g., a 2×6 array, a 2×4 array, etc.), a hexagonallypacked cylindrical array (e.g., with an uppermost row of three fibers, asecond row of four fibers, a third row of three fibers, and a bottom rowof two fibers), or the like. Potential benefits of arranging multipleoptical fibers in multi-dimensional configurations are that theresulting arrangement may be narrower and/or more flexible in at leastsome directions than a one-dimensional array, thereby enabling segmentsincorporating multi-dimensional configurations to be more easily routedthrough small openings and/or relatively tight-radius bends.

A first example of a plurality of optical fibers transitioning from amulti-dimensional configuration to a one-dimensional array and useablefor forming an optical fiber fan-out assembly is provided in FIGS. 16Aand 16B. FIGS. 16A and 16B provide perspective and side elevationalviews, respectively, of a fiber arrangement 200 that includes aplurality of optical fibers 208 extending through a larger pitch firstsegment 202, a smaller pitch second segment 204, and a transitionsegment 206. In the first segment 202, each optical fiber 208 is encasedin a buffer material 210, and the optical fibers 208 are arranged in a3×4 array. Centers of adjacent optical fibers 208 in each row of the 3×4array have a first pitch. Each buffer 210 terminates at a buffer end 212corresponding to a beginning of the transition segment 206. In thesecond segment 204, each optical fiber 208 is devoid of a buffer, andthe optical fibers 208 are arranged in a 1×12 array with centers ofadjacent fibers having a second pitch that is smaller than the firstpitch. In the transition segment 206, each optical fiber 208 is devoidof a buffer, and the optical fibers 208 transition from themulti-dimensional array matching the configuration of the first segment202 to a smaller pitch one-dimensional array matching the configurationof the second segment 204.

As shown in FIG. 16C, at least a central portion of the fiberarrangement 200 of FIGS. 16A and 16B may be overcoated with anovercoating material 214 to form an overcoated fiber arrangement 200A.The overcoating material 214 extends over the entire transition segment206, and over portions of each of the first segment 202 and the secondsegment 204. A first end 216 of the overcoating material 214 extendsover buffer material 210 and terminates in the first segment 202, whilea second end 218 of the overcoating material 214 extends over bareoptical fibers 208 and terminates in the second segment 204. In certainembodiments, uncoated ends 219 of the optical fibers 208 extendingbeyond the second end 218 of the overcoating material 214 may be massfusion spliced with an array of optical fibers of an optical ribbon (notshown) and a resulting fusion splice region may be overcoated withadditional overcoating material (optionally having the same compositionas the overcoating material 214).

A second example of a plurality of optical fibers transitioning from amulti-dimensional configuration to a one-dimensional array and useablefor forming an optical fiber fan-out assembly is provided in FIGS. 17Aand 17B. FIGS. 17A and 17B provide perspective and side elevationalviews, respectively, of a fiber arrangement 220 that includes aplurality of optical fibers 228 extending through a larger pitch firstsegment 222, a smaller pitch second segment 224, and a variable pitchtransition segment 226. In the first segment 222, each optical fiber 228is encased in a buffer 230, and the optical fibers 228 are arranged in ahexagonally packed cylindrical array. Each buffer 230 terminates at abuffer end 232 corresponding to a beginning of the transition segment236. In the second segment 224, each optical fiber 228 is devoid of abuffer, and the optical fibers 228 are arranged in a 1×12 array. In thetransition segment 226, each optical fiber 228 is devoid of a buffer,and the optical fibers 228 transition the configuration of the firstsegment 222 to the smaller pitch, one-dimensional array matching theconfiguration of the second segment 224.

As shown in FIG. 17C, at least a central portion of the fiberarrangement 220 of FIGS. 17A and 17B may be overcoated with anovercoating material 234 to form an overcoated fiber arrangement 220A.The overcoating material 224 extends over the entire transition segment226, and over portions of each of the first segment 222 and the secondsegment 224. A first end 236 of the overcoating material 234 extendsover buffer material 230 and terminates in the first segment 222, whilea second end 238 of the overcoating material 234 extends over bareoptical fibers 228 and terminates in the second segment 224. In certainembodiments, uncoated ends 239 of the optical fibers 228 extendingbeyond the second end 238 of the overcoating material 234 may be massfusion spliced with an array of optical fibers of an optical ribbon (notshown) and a resulting fusion splice region may be overcoated withadditional overcoating material (optionally having the same compositionas the overcoating material 234).

In certain embodiments, a method for fabricating a multi-fiber assemblyproviding fan-out functionality comprising multiple steps is provided,and an optical fiber assembly formed by such method is further provided.One step of the method comprises arranging a first segment of a firstplurality of optical fibers in a one-dimensional array having a firstpitch between centers of adjacent optical fibers of the first pluralityof optical fibers. A plurality of optical fiber legs extend from theone-dimensional array at an end of the first segment, each optical fiberleg of the plurality of optical fiber legs includes at least one opticalfiber of the first plurality of optical fibers, and a fiber opticconnector that terminates the at least one optical fiber of the opticalfiber leg. Another step of the method comprises arranging a secondsegment of the first plurality of optical fibers in a one-dimensionalarray having a second pitch between centers of adjacent optical fibersof the first plurality of optical fibers, wherein the second pitch issmaller than the first pitch. The arranging of the first segment and thesecond segment includes defining a transition segment between the firstand second segments, and in the transition segment the one-dimensionalarray comprises a pitch between centers of adjacent optical fibers ofthe plurality of optical fibers that transitions from the first pitchproximate the first segment to the second pitch proximate the secondsegment. Another step of the method comprises encapsulating the firstplurality of optical fibers at least in the transition segment with apolymeric material (optionally by injection molding or dip coating). Inat least a portion of the second segment, the first plurality of opticalfibers extends beyond a boundary of the polymeric material.

In certain embodiments, the foregoing method further comprises forming aholding body encapsulating the first plurality of optical fibers in aportion of the first segment, prior to encapsulating the first pluralityof optical fibers at least in the transition segment with the polymericmaterial. In certain embodiments, the arranging of the second segment ofthe first plurality of optical fibers in a one-dimensional arraycomprises inserting optical fibers of the first plurality of opticalfibers in a fiber sorting fixture. The use of such a fixture mayfacilitate defining a transition segment including formation of S-bends,each including a maximum bend radius of about 22.7 mm, in at least thetwo outermost optical fibers of the array of optical fibers in thetransition segment. In certain embodiments, prior to the arranging ofthe first segment, each optical fiber of the first plurality of opticalfibers may be embodied in a respective connector pigtail that furtherincludes a respective fiber optic connector terminating the opticalfiber, wherein the optical fiber optionally comprises a tight bufferedfiber secured to the fiber optic connector. In embodiments in which eachoptical fiber comprises a tight buffer, the method may further comprisestripping a portion of each tight buffer from the respective opticalfiber of the first plurality of optical fibers to expose lengths ofcoated optical fibers that each have a diameter of 250 μm or less, priorto the arranging of the second segment of the first plurality of opticalfibers in a one-dimensional array. In certain embodiments, the methodfurther comprises stripping a coating from each optical fiber of thefirst plurality of optical fibers in at least a portion the secondsegment to form bare glass. Bare glass sections of optical fibers of thefirst plurality of optical fibers may be mass fusion spliced to bareglass ends of optical fibers of a second plurality of optical fibers toform a plurality of fusion splices. Thereafter, the plurality of fusionsplices, the bare glass stripped sections optical fibers of the firstplurality of optical fibers, and the bare glass sections of opticalfibers of the second plurality of optical fibers, may be encapsulatedwith a polymeric material. In certain embodiments, the second pluralityof optical fibers may comprise an optical fiber ribbon having an endterminated with a multi-fiber connector.

Example

Tight buffered sections of twelve SC-type connector pigtails are bundledtogether with a bundling body using the method described previouslyherein, with unbuffered optical fibers extending beyond the bundlingbody. TECHNOMELT® PA 6208 polyamide material is used to form thebundling body. One set of six connectors has a pigtail length of 75 mm,and another set of six connectors has a pigtail length of 50 mm. Thebuffer material is PVC, which has a lower melting temperature than thepolyamide bundling body material, but a dip coating process for applyingthe bundling body is completed in a short time and the buffers remainintact after formation of the bundling body. Steps in forming theholding body and the transition segment, then encapsulating thetransition segment and the second segment, are performed as describedabove in connection with FIGS. 8-11. The same polyamide material is usedto form the bundling body is also used to form the holding body and toencapsulate the transition and second segments. At an end of the secondsegment, an initially ribbonized fiber is stripped of polymeric material(e.g., polymeric encapsulant and polymer coating), cleaned, and cleavedusing standard ribbon fiber termination tools. The completed opticalfiber fan-out assembly is consistent with the assembly illustrated inFIG. 13, except for the presence of two groups of six optical fiber legsof different lengths.

The above-described optical fiber fan-out assembly is mass fusionspliced to a MPO connector pigtail, with previously stripped (bare)portions and the splice region encapsulated using the same polyamidematerial used for formation of the bundling body, holding body, andmulti-segment encapsulation. The resulting cable assembly is consistentwith the assembly illustrated in FIG. 15, except for the presence of twogroups of six optical fiber legs of different lengths. The entire cableassembly is flexible. Both the transition segment and the splice region(which are devoid of any housings or strength members) can be bent at aradius down to 25 mm without incurring measurable macro bend loss.

Those skilled in the art will appreciate that modifications andvariations can be made without departing from the spirit or scope of theinvention. Since modifications, combinations, sub-combinations, andvariations of the disclosed embodiments incorporating the spirit andsubstance of the invention may occur to persons skilled in the art, theinvention should be construed to include everything within the scope ofthe appended claims and their equivalents. The claims as set forth beloware incorporated into and constitute part of this detailed description.

It will also be apparent to those skilled in the art that unlessotherwise expressly stated, it is in no way intended that any method inthis disclosure be construed as requiring that its steps be performed ina specific order. Accordingly, where a method claim below does notactually recite an order to be followed by its steps or it is nototherwise specifically stated in the claims or descriptions that thesteps are to be limited to a specific order, it is no way intended thatany particular order be inferred.

What is claimed is:
 1. An optical fiber fan-out assembly comprising: aplurality of optical fibers arranged in a one-dimensional arrayextending through a first segment, a second segment, and a transitionsegment disposed between the first and second segments; a plurality ofoptical fiber legs extending from the one-dimensional array at an end ofthe first segment, wherein each optical fiber leg of the plurality ofoptical fiber legs includes at least one optical fiber of the pluralityof optical fibers and a fiber optic connector that terminates the atleast one optical fiber of the optical fiber leg; and a polymericmaterial encapsulating the plurality of optical fibers in the transitionsegment; a holding body encapsulating the plurality of optical fibers ina portion of the second segment, wherein at least a portion of theholding body is encapsulated by the polymeric material; wherein: in thefirst segment, the one-dimensional array comprises a first pitch betweencenters of adjacent optical fibers of the plurality of optical fibers;in the second segment, the one-dimensional array comprises a secondpitch between centers of adjacent optical fibers of the plurality ofoptical fibers; in the transition segment, the one-dimensional arraytransitions from the first pitch proximate the first segment to thesecond pitch proximate the second segment; and in at least a portion ofthe second segment distal from the transition segment, the plurality ofoptical fibers extends beyond a boundary of the polymeric material. 2.The optical fiber fan-out assembly of claim 1, wherein in the at least aportion of the second segment, the plurality of optical fibers comprisesbare glass optical fibers extending beyond the boundary of the polymericmaterial.
 3. The optical fiber fan-out assembly of claim 1, wherein theplurality of optical fiber legs comprises tight buffered optical fibers,loose tube buffered optical fibers, or jacketed optical fibers.
 4. Theoptical fiber fan-out assembly of claim 1, wherein the fiber opticconnector of each optical fiber leg comprises a simplex connector or aduplex connector.
 5. The optical fiber fan-out assembly of claim 1,wherein: the one-dimensional array has a lengthwise axis, a widthwiseaxis orthogonal to the lengthwise axis, and a thickness axis orthogonalto the lengthwise and widthwise axes; and the polymeric materialencapsulating the plurality of optical fibers in the transition segmenthas a narrow width profile, having a width along the widthwise axis thatis no greater than 2 mm wider at any position than a widthwise extent ofthe plurality of optical fibers in the transition segment at thatposition.
 6. The optical fiber fan-out assembly of claim 1, wherein: theone-dimensional array has a lengthwise axis, a widthwise axis orthogonalto the lengthwise axis, and a thickness axis orthogonal to thelengthwise and widthwise axes; and the polymeric material encapsulatingthe plurality of optical fibers in the transition segment has athickness along the thickness axis that is no greater than 2 mm thickerthan a thickness of the plurality of optical fibers in the transitionsegment.
 7. The optical fiber fan-out assembly of claim 1, wherein: theone-dimensional array has a lengthwise axis, a widthwise axis orthogonalto the lengthwise axis, and a thickness axis orthogonal to thelengthwise and widthwise axes; and in the transition segment: a firstwidthwise dimension corresponding to a maximum widthwise extent of theone-dimensional array varies with position along a lengthwise dimensionof the transition segment; a second widthwise dimension corresponding toa maximum widthwise extent of the polymeric material varies withposition along the lengthwise dimension of the transition segment; thesecond widthwise dimension exceeds the first widthwise dimension at eachposition by a width differential, and the width differential varies withposition along the lengthwise dimension of the transition segment by nomore than about 20%.
 8. The optical fiber fan-out assembly of claim 1,wherein: the one-dimensional array has a lengthwise axis, a widthwiseaxis orthogonal to the lengthwise axis, and a thickness axis orthogonalto the lengthwise and widthwise axes; the second segment comprises anoptical fiber ribbon containing the plurality of optical fibers; and inthe transition segment, the polymeric material encapsulating theplurality of optical fibers provides a flexible support for theplurality of optical fibers, with the transition segment being at least50% as flexible as the optical fiber ribbon in bending about thethickness axis.
 9. The optical fiber fan-out assembly of claim 1,wherein: the plurality of optical fibers includes two outermost opticalfibers of the one-dimensional array, and in the transition segment, thetwo outermost optical fibers each form an S-bend having a minimum bendradius of at least 22.7 mm.
 10. The optical fiber fan-out assembly ofclaim 1, wherein the holding body comprises a material having the samecomposition as the polymeric material.
 11. The optical fiber fan-outassembly of claim 1, wherein each optical fiber of the plurality ofoptical fibers in the first segment comprises a tight buffered opticalfiber.
 12. The optical fiber fan-out assembly of claim 11, furthercomprising a bundling body encapsulating a plurality of the tightbuffered fibers in a portion of the first segment.
 13. The optical fiberfan-out assembly of claim 1, being devoid of a housing and devoid of astrength member arranged in, on, or around the polymeric materialencapsulating the plurality of optical fibers in the transition segment.14. The optical fiber fan-out assembly of claim 1, wherein the firstpitch is 900 μm, and the second pitch is 250 μm or less.
 15. The opticalfiber fan-out assembly of claim 1, wherein the polymeric materialcomprises a melt-flow thermoplastic adhesive.
 16. The optical fiberfan-out assembly of claim 1, wherein the plurality of optical fiberscomprises at least four optical fibers.
 17. The optical fiber fan-outassembly of claim 1, wherein each optical fiber leg is devoid of afurcation tube.
 18. A fiber optic cable assembly comprising: a firstplurality of optical fibers arranged in a one-dimensional arrayextending through a first segment, a second segment, and a transitionsegment disposed between the first and second segments, wherein eachoptical fiber of the first plurality of optical fibers includes a firstbare glass section along an end of the second segment distal from thetransition segment; a plurality of optical fiber legs extending from theone-dimensional array at an end of the first segment, wherein eachoptical fiber leg of the plurality of optical fiber legs includes atleast one optical fiber of the first plurality of optical fibers and afiber optic connector that terminates at least one optical fiber of theoptical fiber leg; a first polymeric material encapsulating the firstplurality of optical fibers in the transition segment; wherein: in thefirst segment, the one-dimensional array comprises a first pitch betweencenters of adjacent optical fibers of the first plurality of opticalfibers; in the second segment, the one-dimensional array comprises asecond pitch between centers of adjacent optical fibers of the firstplurality of optical fibers; and in the transition segment, theone-dimensional array transitions from the first pitch proximate thefirst segment to the second pitch proximate the second segment; a secondplurality of optical fibers arranged in a one-dimensional array, whereineach optical fiber of the second plurality of optical fibers includes asecond bare glass section; a plurality of fusion splices connecting endsof the first bare glass sections to ends of the second bare glasssections; and a second polymeric material encapsulating the plurality offusion splices, the first bare glass sections, and the second bare glasssections.
 19. The fiber optic cable assembly of claim 18, furthercomprising a multi-fiber connector terminating an end of the secondplurality of optical fibers that is opposite the ends of the second bareglass sections.
 20. The fiber optic cable assembly of claim 18, whereinthe first polymeric material comprises a material having the samecomposition as the second polymeric material.
 21. The fiber optic cableassembly of claim 18, wherein each optical fiber of the first pluralityof optical fibers in the first segment comprises a tight buffered fiber,and the fiber optic cable assembly further comprises a bundling bodyencapsulating the tight buffered fibers in a portion of the firstsegment.
 22. The fiber optic cable assembly of claim 18, being devoid ofany housing or strength member arranged in, on, or around one or moreof: (i) the first polymeric material encapsulating the first pluralityof optical fibers in the transition segment, or (ii) the secondpolymeric material encapsulating the plurality of fusion splices, thefirst bare glass sections, and the second bare glass sections.
 23. Thefiber optic cable assembly of claim 18, each optical fiber of the firstplurality of optical fibers in the first segment comprises a tightbuffered optical fiber.
 24. The fiber optic cable assembly of claim 18,wherein each optical fiber leg is devoid of a furcation tube.
 25. Anoptical fiber fan-out assembly comprising: a plurality of optical fibersarranged in a one-dimensional array extending through a first segment, asecond segment, and a transition segment disposed between the first andsecond segments; a plurality of optical fiber legs extending from theone-dimensional array at an end of the first segment, wherein eachoptical fiber leg of the plurality of optical fiber legs includes atleast one optical fiber of the plurality of optical fibers and a fiberoptic connector that terminates the at least one optical fiber of theoptical fiber leg; and a polymeric material encapsulating the pluralityof optical fibers in the transition segment; wherein: theone-dimensional array has a lengthwise axis, a widthwise axis orthogonalto the lengthwise axis, and a thickness axis orthogonal to thelengthwise and widthwise axes; and the polymeric material encapsulatingthe plurality of optical fibers in the transition segment has a narrowwidth profile, having a width along the widthwise axis that is nogreater than 2 mm wider at any position than a widthwise extent of theplurality of optical fibers in the transition segment at that position;and wherein: in the first segment, the one-dimensional array comprises afirst pitch between centers of adjacent optical fibers of the pluralityof optical fibers; in the second segment, the one-dimensional arraycomprises a second pitch between centers of adjacent optical fibers ofthe plurality of optical fibers; in the transition segment, theone-dimensional array transitions from the first pitch proximate thefirst segment to the second pitch proximate the second segment; and inat least a portion of the second segment distal from the transitionsegment, the plurality of optical fibers extends beyond a boundary ofthe polymeric material.